This invention relates to particular fats and fat blends, and methods for their manufacture or genetic selection/engineering, and use in foods. Consumption of such fats in appropriate amounts stabilizes or lowers the low density lipoprotein cholesterol (LDL or LDL-C) concentration and increases the high density lipoprotein cholesterol (HDL or HDL-C) concentration in human serum. This invention also relates to filled dairy products and to a method for preventing the development of off-flavors in these products.
The description and references herein are provided solely to assist the understanding of the reader. None of the information or references are admitted to be prior art to the present invention.
Coronary heart disease (CHD) is the major cause of death in the USA and other affluent nations. Plasma cholesterol, more specifically the LDL/HDL ratio, is highly correlated with risk of CHD as documented by Willett and Sacks, 324 N. Eng. J. Med. 121, 1991. The accumulation of LDL in the arterial intima is thought to lead to its oxidation, which in turn results in cascading events that induce arterial occlusion and thrombosis. High concentrations of HDL appear to block LDL oxidation and reduce the atherogenic potential of LDL. Thus, dietary means which decrease the LDL/HDL ratio (or increase the HDL/LDL ratio), especially means which would increase HDL, are desirable. Perlman and Hayes, U.S. Pat. No. 5,382,442 describe modified fat compositions and methods for decreasing total serum cholesterol while simultaneously decreasing the LDL/HDL serum cholesterol ratio. This ratio decreased as both the LDL and HDL concentrations decreased. The net LDL/HDL ratio in the serum decreased only because the LDL cholesterol concentration decreased by a greater factor than serum HDL with the dietary use of a fat-oil blend which included one to ten parts by weight cholesterol-reduced animal fat containing myristic acid, and one part by weight vegetable oil containing linoleic acid.
Within the past three years several authors have collected and analyzed a large number of independent metabolic studies relating to the effect of saturated, monounsaturated, and polyunsaturated fatty acids in the diet on serum LDL and HDL cholesterol levels. These studies have included the techniques of multiple regression analysis to examine LDL and HDL levels versus dietary intake of each group of fatty acids as separate variables expressed as the percentage of dietary energy, i.e., the total daily calorie intake of individuals in the studies.
Mensink and Katan (12 Arteriosclerosis and Thrombosis 911, 1992) made the following conclusions; “Replacement of saturated by unsaturated fatty acids raised the HDL to LDL cholesterol ratio, whereas replacement by carbohydrates had no effect. Thus, under isocaloric metabolic-ward conditions the most favorable lipoprotein risk profile for coronary heart disease was achieved if saturated fatty acids were replaced with unsaturated fatty acids, with no decrease in total fat intake.” Hegsted et al. (57 Am. J. Clin. Nutr. 875, 1993), combined data from 155 human trials in which LDL and HDL cholesterol measurements were available. With regard to fatty acids and cholesterol in the diet, the authors state in their published abstract, “1) saturated fatty acids increase and are the primary determinants of serum cholesterol, 2) polyunsaturated fatty acids actively lower serum cholesterol, 3) monounsaturated fatty acids have no independent effect on serum cholesterol and 4) dietary cholesterol increases serum cholesterol and must be considered when the effects of fatty acids are evaluated. More limited data on low density lipoprotein cholesterol (LDL-C) show that changes in LDL-C roughly parallel the changes in serum cholesterol but that changes in high density lipoprotein cholesterol cannot be satisfactorily predicted from available data.” Within this cited article, Hegsted et al. show that LDL levels increase an average of 1.74 mg/dl for each 1% increase in dietary energy represented by saturated fatty acids, while LDL levels decrease an average of 0.77 mg/dl for the corresponding amount of polyunsaturated fatty acids. Referring to the possibility of predicting changes in HDL levels in the serum, these same authors state, “It does not appear possible to develop an equation that predicts changes in HDL-C satisfactorily” and, “The errors in the regression coefficients are large; hence, little reliance should be placed on the equation.” These authors calculate a very modest increase in HDL-C correlating with a dietary increase in either saturated or polyunsaturated fatty acids (0.43 mg/dl for a 1 increase in dietary energy represented by saturated fatty acids and 0.22 mg/dl for the corresponding amount of polyunsaturated fatty acids). This indicates that one would expect that for saturated fatty acids, the much smaller increase in HDL (0.43) versus LDL (1.74) per dietary energy, would typically result in a decrease in the HDL/LDL ratio as the saturated fatty acids are increased. On the other hand, the Hegsted et al. and the Mensink and Katan calculations would predict that an increase in the proportion of dietary polyunsaturated fatty acids at the expense of saturated fatty acids would increase the HDL/LDL ratio because this dietary increase caused a large decrease in LDL (approximately 2 mg/dl) and only a small proportional decrease in HDL (approximately 0.2 mg/dl). By comparison, the overall HDL/LDL serum ratios in these studies ranged from approximately 0.25 to 0.50.
Fat blends which include saturated vegetable fats in combination with polyunsaturated vegetable oils have been noted for dietary and/or cooking use. For example, Choi et al., 24(1) Lipids 45, 1989, describe cholesterol synthesis in rats with the feeding of safflower oil or linseed oil blended with palm olein in purified diets containing 10% fat. Suzuki et al.(Jpn. Kokai Tokkyo Koho JP 01, 262, 753>89, 262, 753! 19 Oct. 1989), describe the use of 40–90% natural palm oil and 60–5% natural vegetable oil in deep frying. Lim et al., (39(12) Yukagaku 1045, 1990) describe the increased oxidative stability of soybean oil blended with crude or refined palm oil or refined palm kernel oil. Murakami et al., (41 (3) Yukagahu 196, 1992) describe the feeding of soybean oil blended with an equal weight of palm stearin in diets containing 20% fat in which cholesterol metabolism was monitored in rats. Kajimoto et al., (44(6) Nippon Eiyo, Shokuryo Gakkaishi 499, 1991) describe the blending of soybean oil or rapeseed oil with palm oil, and the blending of soybean oil, rapeseed oil and palm oil to enhance the oxidative stabilities of the polyunsaturated oils. Han et al., (23 (4) Han'guk Sikp'um Kwahakhoechi 465, 1991) describe the stabilization of soybean oil against thermal and oxidative degradation by blending with an equal or greater proportion of palm oil.
The public awareness of an increased risk of cardiovascular disease associated with dietary consumption of substantial amounts of fats rich in saturated fatty acids and cholesterol has led to an overall reduction in fat intake and an increased demand for foods containing unsaturated rather than saturated fatty acids. A multiplicity of clinical studies have shown that when certain dietary levels of saturated fats are replaced by unsaturated fats, one's total serum cholesterol level decreases. Since the milkfat, i.e., butter in dairy products contains approximately 0.22%–0.25% by weight cholesterol, more than 60% saturated fatty acids, and only approximately 4% polyunsaturated fatty acids, health-conscious individuals often prefer to consume dairy products in which the milkfat content has been reduced, eliminated, or replaced with vegetable oil.
Liquid milks are divided into various product categories based upon their weight percentage fat contents. Regular whole milk contains approximately 3.25% milkfat. Based upon an 8 fluid ounce (244 g) serving size, this corresponds to 7.9–8 grams (abbreviated g) milkfat and 35 milligrams (abbreviated mg) cholesterol per serving A “reduced fat” product must contain no more than 75% of the fat present in the original product, while a “low fat” product must contain no more than 3 g fat per serving. Thus, for milk having a 244 g serving size, a 2% milkfat-containing milk is termed a reduced fat product, while a 1% milkfat-containing milk is termed a low fat milk. On the other hand, to meet the current definition of “skim”, “non-fat”, or “fat-free” milk (having a 245 g serving size), the milk must contain less than 0.2% by weight milkfat, i.e., less than 0.5 g per serving, and less than 5 mg cholesterol per serving.
Filled milk is defined as skim milk which has been enriched in fat content by addition of vegetable oil. The literature on filled dairy products includes both liquid products and dried products which are reconstituted by addition of water. A number of patents describe the substitution of vegetable oils for milkfat in filled milks, to obtain nutritionally improved products which are lower in saturated fat and cholesterol. However, these modified dairy products often have an altered or unnatural flavor and mouthfeel. Howard, U.S. Pat. No. 2,659,676, describes a dried milk product prepared from skim milk and palm fat. The vegetable fat and lecithin are added to heated skim milk, which is then pasteurized, homogenized and spray-dried. Stein et al., German Offenlegungsschrift 2,444,213, describes a dried milk containing a reduced proportion of saturated fat in which polyunsaturated fat is mixed with evaporated concentrated milk which is then homogenized and dried. Kneeland, U.S. Pat. No. 3,011,893, describes a reconstituted milk prepared from powdered skim milk, vegetable oil, and water, in which a mixture of the skim milk and water is heated, vegetable oil is added, and the mixture is homogenized and pasteurized. Bundus, U.S. Pat. No. 3,488,198, describes a filled milk prepared from skim milk solids, water, fat, and a water-in-oil emulsifier. The fat may be any one of a variety of vegetable fats and oils or hydrogenated vegetable oils including coconut oil, palm oil, cottonseed, corn, soybean, peanut, olive oil, and hydrogenated derivatives of several of these oils. Arndt, U.S. Pat. No. 3,843,828, describes a simulated milk product which includes vegetable protein, whey and hydrogenated vegetable oil. Bookwalter et al., U.S. Pat. No. 4,842,884, describes a milk concentrate prepared from nonfat dry milk and vegetable oil.
Vegetable oils are also used as vehicles for adding vitamins and minerals to fortify dairy products. For example, Karinen, U.S. Pat. No. 4,803,087, describes vitamin A and D fortification of milk using an aqueous emulsion of vegetable oil and an emulsifier.
In recent years, several patents have described the composition and preparation of improved flavor vegetable oil-containing filled milks which are asserted to possess the flavor and mouthfeel of whole milk. It is suggested that these filled milks are healthier than ordinary milk due to the absence of cholesterol and the significantly lower saturated fat content. For example, Arcadipane, U.S. Pat. No. 5,393,551, describes a filled milk having a butterfat substitute providing the taste and mouthfeel of an unmodified milk with the same amount of butterfat (ranging from 1% to 4%). The butterfat substitute includes 66%–98% of a partially hydrogenated soybean oil whose major fatty acids are present in approximately the following proportions: saturated fatty acids: palmitic 11%, stearic 14%; monounsaturated fatty acid: oleic 68%. A small proportion of the polyunsaturated fatty acids, linoleic 6%, and linolenic 0.1%, are also present. Arcadipane states that a filled milk assembled from skim milk, mono- and diglyceride emulsifiers, and the above partially hydrogenated soybean oil has an extended shelf life compared to ordinary milk, and may be stored under the same conditions as ordinary milk. While the pre-hydrogenated soybean oil contains approximately 63% polyunsaturated fat, this level is reduced to only 2% to 8% after hydrogenation. Strong et al., U.S. Pat. No. 5,580,600, describes a filled milk containing principally monounsaturated vegetable oil. A high oleic acid-containing vegetable oil such as rapeseed or sunflower oil containing at least 70% oleic acid, and no more than 12% by weight polyunsaturated linoleic acid and no more than 0.5% linolenic acid is combined with skim milk, an emulsifier, a polysaccharide modifier, and a carbohydrate gel stabilizer for the emulsion. Strong et al. states that a high proportion of oleic acid-rich vegetable oil is used to avoid the problems of rancidity and off-flavors which develop after relatively short periods of storage when a substantial proportion of the added vegetable oil is in the form of polyunsaturated fats and oils. Despite the rancidity problem associated with polyunsaturated vegetable oils, Kahn et al., U.S. Pat. No. 5,063,074, describes a low cholesterol, low fat, filled milk containing polyunsaturated vegetable oil, stated to have the taste and mouthfeel of whole or 2% milkfat-containing milk. The milk contains skim milk and 1%–5% of a premix (milkfat substitute) which includes 50%–70% non-tropical (polyunsaturated) vegetable oil such as soybean oil, 6%–10% of a non-lauric emulsifier, and a substantial proportion of flavoring agent (6%–10%) and food gum (15%–20%). The flavoring agent, which is a requirement of these milks, is most preferably 70%–90% natural milk distillate plus natural vanilla.
Light-induced alterations in the chemistry of conventional milkfat-based dairy products have been recognized and studied for many years. These alterations which, it has been suggested, may involve protein (amino acid) and lipid reactions, lead to the formation of taste changes which are invariably undesirable. When most dairy products, including regular milkfat-based milks, are stored under artificial lighting, e.g., fluorescent lighting, such flavor alterations occur gradually over the life of the product. The level of off-flavor development depends upon many factors including the type of lighting, product proximity to the light source, length of exposure and fat level of the milk. For example, regular milk containing 1% by weight milkfat, when stored in a translucent plastic jug, may show slight to moderate oxidized flavor development after 12 hours of typical retail fluorescent lighting exposure (200 footcandle exposure, see Example 2 below). Light can also destroy a number of important vitamins in milk with varying speed. Several light-susceptible vitamins include vitamin A (retinol), its provitamin, beta-carotene, vitamin B2 (riboflavin) and vitamin C (ascorbic acid). The photosensitivity of vitamins A and B2 in milk has been examined. The level of vitamin A in milk decreases rapidly upon exposure to visible (violet) light below a wavelength of 415 nm and to a lesser degree at wavelengths between 415 nm and 455 nm, while vitamin B2 is degraded by light between the wavelengths of 415 nm and 455 nm (blue-violet). The rapidity of vitamin breakdown depends upon the intensity, duration and wavelength of light, the product storage temperature, and light transmittance through the product and its packaging. Skim milk, for example, is more transparent than regular milk (which contains emulsified fat), and its vitamins are therefore more susceptible to photodegradation.
Over the years, a variety of containers have been developed, which protect milks from the effects of natural and artificial light. These containers include printed paperboard cartons and pigmented and/or multi-layered plastic bottles. One such container is a white pigmented high density polyethylene (HDPE) jug recently brought to market by the H.P. Hood Company (Chelsea, Mass). Tests of the one gallon and half gallon sizes of this so-called “Light-Block Bottle™” have shown that they block at least 85% to 90% of incident light between the wavelengths of 300 nm and 700 nm. At 400 nm and below, these containers block essentially all light.